Polyimide (PI) is a macromolecular material including strong mechanical properties, heat endurance under high temperature, and electric insulating properties. Now, polyimide has become an important material for manufacturing flexible printed circuits (FPC). For instance, when the manufacturers manufacturing the flexible printed circuits, circuit diagrams are designed onto the flexible copper clad laminates (FCCL), and then the circuit diagrams are covered by the polyimide films including adhesives so as to manufacture the flexible copper clad laminates covered with the polyimide films. Since printed circuit boards are important components in fields of electronic products, polyimide films have become necessary materials for manufacturing electronic products.
Since the great competence of the consuming of electronic products in daily lives, consumers have more demands on the appearance or color of the electronic products. While black color has become a fashion of mobile phones and notebooks, electronic products having a black appearance have become a symbol of fashion. On the other hand, the designs of electronic products have become more complicated with the development of technologies. Since the quality of the electronic products depends on the circuit diagrams on the printed circuit boards, the circuit diagrams have become the core technique that need to be protected. For the flexible copper clad laminates covered with the polyimide films, the polyimide films on the copper clad laminates are usually yellow, the derivative colors, or other colors with high transparency. Therefore, circuit designs on the cable layer on printed circuit boards are easily decoded or plagiarized because the transparency of the flexible copper clad laminates covered with the polyimide films. Moreover, the market of the products and the running of the companies are affected.
Therefore, now designers need to solve the problems met in the previous polyimide films that the circuit diagrams are easily decoded according to the transparency of the polyimide films.